Materials testing grip



April 27, 1943. R. L. TEMPLIN- MATERIAL TESTING GRIP 2 Sheets-Sheet 1 .INVENTOR RICHARD L. TEMPLIN Filed Nov. 14, 1941 ATTORNEY R. L. TEMPLIN MATERIAL TESTING GRIP Filed NOV. 14, 1941 -2 Sheets-Sheet 2 'INVENTOR RIC HARD L. TEMPLIN ATTORNEY Patented Apr. 27, 1943 UNITED STATES FATENT OFFICE MATERIALS TESTING GRIP Richard L. Templin, New Kensington, Pa. Application November 14, 1941, Serial No. 419,181

4 Claims.

This invention relates generally to grips for materials testing machines and it is one object to provide an improved grip that is particularly adapted to test specimens which have a substantially uniform cross-sectional area throughout their length such for instance as is usually employed in testing strip material although the principles of my invention are applicable to different kinds of specimens.

Heretofore grips have tended to create an excessive stress concentration at the points where the grip jaws initially engage the specimen thereby tending to break the specimen at this point rather than at its normal place of rupture somewhere midway between the upper and lower sets of jaws. A more specific object of my invention is to overcome this difiiculty of excessive stress concentration at the juncture of initial engagement between the specimen and jaws and at the same time insure adequate gripping action of the specimen. In accomplishing this and other objects I have specifically provided an improved grip whose elastic behavior'under various total loads will eliminate abnormal stress concentrations that tend to be created in the specimen by the grips. v

Another object is to accomplish desirable elastic behavior of the grips while at the same time insuring that the grips have the necessary degree of rigidity and durability for firmly clamping a specimen.

Other objects and advantages will be more ap-- parent to those skilled in the art from the following description of the accompanying drawings in which:

Fig. 1 is a front elevation of my improved grip with a portion broken away to show details of construction Fig. 2 is a back view of my improved grip;

Fig. 3 is a substantially horizontal section taken generally on the line 3-3 of Fig. 1; and

Fig. 4 is a transverse section taken substantially on the lines 4-4 of Figs. 1 and 3.

My improved grip comprises, as herein specifically disclosed for purposes of illustration, a frame I having a cross member 2 and downwardly and inwardly inclined side pieces 3 and 4, these three portions being connected by a relatively thin back wall 5, Fig. 3. The side pieces 3 and 4 are formed with inner surfaces 6 and 1 converging toward the other end of the frame thereby to support usual wedge grip jaws 8 and 9 which may have any suitable type of grip engaging surfaces. The jaws are held in position by keeper strips or lips l and H seated in suitable recesses such as l2, Fig. 3, in the front face of the side pieces and held thereto by suitable screws. It will be observed in particular that the side pieces 3 and. 4 are not connected together across their front sides as they are at located solely on only one side of the grip frame specifically at the back side.

As a result of my improved open type elastic arrangement when load is applied to a specimen the lateral wedging force of-the grips will tend .to cause the lower front side of the frame to spread apart, the back flange I 4 maintaining this elasticity within desired limits. While the lower front end of the frame tends to be spread apart, yet the upper end of the frame is more resistant to spreading action by reason of the cross frame member 2 being connected across the entire horizontal cross-sectional area of the upper ends of side members 3 and 4. In other words, the cross member lies in the plane of the side pieces by being of the same total depth as the depth of side pieces 3 and 4 as is shown in Fig. 4. Hence the degree of resistance against spreading increases from the toes I6 of the grips toward the upper ends thereof with the result that the specimen is more firmly gripped at the upper ends of the jaws than at. the toe ends thereof and accordingly there is less tendency to create stress concentrations at the point where the specimen initially entersthe jaws at the toes I6. It will be understood that two sets of grips are used in testing a specimen and hence reference to the upper or lower ends of the jaw or frame is merely for convenience. In either case the jaws are pulled by a shaft 30 screwed into the head 2.

The jaws may be lifted or lowered in the same manner as in my Patent 1,872,047 of which this present invention is an improvement. Briefly, however, the jaws are lifted by a hand operated shaft I1 suitably journalled in side piece 3 and provided with a, lever [B for moving a guide plate l9 up and down. This guide plate engages a pair of jaw pins 20 and 2| extending through suitable slots 22 and 23 in the back wall 5. A pin 25 connects lever [B with guide plate i9 and also projects into a vertical guide slot 24. Normally pins and 2| move only in the inclined portions of slots 22 and 23, Fig. 2, but if it is desired to hold the jaws open then a filler pin 26 normally disposed in the upper end of slot 24 is removed by merely pressing upon a spring pressed shaft 21, Fig. 4, whereupon pin 25 can move to the uppermost end of slot 24 to bring pins 20 and 2|, Fig. 2, into alignment withrecesses 28 and 29 into which pins 20 and 2| would move to support the jaws in their uppermost position.

From the foregoing disclosure it is seen that I have provided an improved grip that is not only adapted to function in a very efiective and emcient manner especially with specimens of substantially uniform cross-sectional area throughout their length but also is relatively simple and inexpensive in initial construction and maintenance.

It will of course be understood that various changes in details of construction and arrangement of parts -may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

l. A wedge grip for clamping test specimens comprising, in combination, a frame having side pieces connected at one end by a cross member, the other end of said side pieces being connected together by a, lateral flange disposed only at the back side of said side pieces whereby the lower end of the grips has a higher degree of elasticity than the upper end, a tapered recess formed between said side pieces and converging toward the flanged end of said framewith the front side of said recess being open, and gripping jaws in said recess.

2. A wedge grip for clamping test specimens comprising, in combination, a frame having side pieces connected at one end by a cross member lying in the plane of said side pieces and forming a tapered recess converging toward the other end of said side pieces, the other end of said side pieces being connected together by a lateral flange disposed only at the back side of said side pieces whereby the lower end of the grips has a higher degree of elasticity than the upper end, the back of said recess being closed by a wall and the front being open, and a pair of gripping jaws vertically movable in said recess so as to be opened or closed as they slide over the inclined walls of said tapered recess.

3. A wedge grip for clamping test specimens, comprising, in combination, a frame having side pieces connected at one end by a cross member lying in the plane of said side pieces and forming a tapered recess converging toward the other end of said side pieces, the other end of said side pieces being connected together by a lateral flange disposed only at the back side of said side pieces whereby the lower end of the grips has a higher degree of elasticity than the upper end, the back of said recess being closed by a wall and the front being open, a pair of gripping jaws movable lengthwise in said recess so as to be opened or closed as they slide over the inclined walls of said tapered recess, and lips secured to the front side of said side pieces and partially overlapping said jaws to hold the same in said recess.

4. A wedge grip for clamping test specimens comprising, in combination, a frame having a recess with guiding surfaces converging as they approach an end of said frame, said guiding surfaces being flat in transverse and longitudinal directions, gripping jaws movable lengthwise in said recess and adapted to be supported against said guiding surfaces, and said frame having means whereby the lower end of said frame has a higher degree of lateral elasticity than the upper part thereof so that a specimen is gripped more firmly near its end than at the part where it; emerges from said jaws.

' RICHARD L. TEMPLIN. 

